DBSAR is an airborne synthetic aperture radar developed by NASA to estimate biomass. It uses digital beamforming to implement advanced scanning modes not possible with conventional SARs. DBSAR's architecture includes an 8-channel phased array antenna, reconfigurable waveform generator, and real-time processor. Initial flights were conducted in 2008 over forests, and field measurements were collected to correlate radar backscatter to biomass. Ongoing work involves biomass retrieval algorithms using DBSAR and interferometry techniques.

1. DigitalBeamformingSynthetic ApertureRadar For Biomass Estimation Rafael F. Rincon, Guoqing Sun, TemilolaFatoyinbo, Jon Ranson and Paul Montesano NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA rafael.rincon@nasa.gov Phone: (301) 614-5725. Fax: (301) 286-1810 July 26, 2010

3. The DBSAR Concept

4. System Architecture

5. Operational Modes

6. Biomass Retrieval Efforts

8. The amount of carbon in above ground vegetation, especially forests, is poorly understood because of the difficulty in acquiring sufficient on-ground measurements of biomass across the diversity of vegetated ecosystems.

10. DBSAR combines digital beamforming, reconfigurable waveform generation, and real-time processing in order to enable multi-mode radar techniques not possible with conventional SARs.

11. DBSAR's highly innovative architecture provide the means to implement and demonstrate advanced SAR techniques that can provide the needed data for biomass studies.

13. Transmit modules feature digital phase steering and amplitude taper

14. Phased array antenna has 64 active microstrip patch elements

15. DBSAR was designed for operation on board of the NASA P3 aircraft Waveform Generator / Digital Beamformer Processor A/D A/D A/D A/D A/D A/D A/D A/D REU T/R T/R T/R T/R T/R T/R T/R T/R Antenna

17. Custom design

18. Three Stratix II FPGAs

19. Eight A/D converters

20. Six SRAMs

21. ARM microcontroller

22. 1-Gb Ethernet interface

23. Size (cm): 17 x 24 x 4

24. Power: 94 W maxMixed signal board Digital signal board

25. System Architecture Main Parameters R A D A R A N T E N N A M I S C DBSAR Calibration in Anechoic Chamber

26. System Architecture Main Features Summary Performs 1-Dimensional scanning (across track in nominal configuration). Capable of sequential polarimetricoperation (HH,VV,VH). (New) Employs software defined radar functions: waveform, T/R taper, digital In-phase and quadrature (I&Q) generation, digital filtering, etc… Implements real-time onboard processing. Supports In-phase and quadrature (I&Q) high data rate acquisition mode. Capable of adjustable transmitter illumination from narrow-beamwidth(high-gain) beam steering to wide-beamwidthillumination. Capable of in-flight reconfigurable waveform generation Employs noise source and closed loop calibration schemes Uses real-time data monitoring through a customized graphical interface unit.

31. The beam illuminates entire field of view

32. Signal returns are collected with the full aperture

33. Several beams are synthesized simultaneously

36. The beam illuminates a single swath

37. Signal returns are collected with the full aperture

38. Selected beam is synthesized on receive

40. Biomass Retrieval Efforts Evaluation of DBSAR and PALSAR Images over the Delmarva Peninsula. Biomass Field measurements over DBSAR mapped areas. Correlation between DBSAR backscatter and ground truth biomass.

41. Biomass Retrieval Efforts Image calibration and evaluation using PALSAR PALSAR DBSAR

42. Biomass Retrieval Efforts Wallops Biomass Field Campaign

43. Biomass Retrieval Efforts Wallops Biomass Field Campaign Coastal plain mixed forest (loblolly pine, hardwood spp.) Mature forest Understory varied: shrub regeneration open 10 m circular plots dGPS location of plot center Trees > 10cm DBH: DBH, species collected

44. Biomass Retrieval Efforts Wallops Biomass Field Campaign

46. Results from the DBBSAR first campaign indicated a successful performance of the radar system and its potential benefits for biomass studies.

47. DBSAR was recently upgraded with polarimetric operation (HH,VV,VH) which enhances the science capability of the system.

48. DBSAR’s next flight campaign is schedule in the summer 2011 when the system will be used to map forests over the US east coast.

51. Transmit channels include programmable attenuators and phase shifter.

52. Receive channels amplify and condition and signal returns .

53. Performs internal calibration by sampling 1) the transmit signal and 2) the signal from a noise source.Single Channel

54. End of Presentation LIS in Anechoic Chamber DBSAR Processor Graphical User Interface Chirp Spectrum Reconfigurable Algorithms Chirp Signal Generator Rack mount Host computer

55. Derived from Jenkins et al. 2003